DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding.

Ilya Nifant'Ev,Pavel Ivchenko

doi:10.3390/polym11122078

Abstract

Organocatalysis is highly efficient in the ring-opening polymerization (ROP) of cyclic esters. A variety of initiators broaden the areas of organocatalysis in polymerization of different monomers, such as lactones, cyclic carbonates, lactides or gycolides, ethylene phosphates and phosphonates, and others. The mechanisms of organocatalytic ROP are at least as diverse as the mechanisms of coordination ROP; the study of these mechanisms is critical in ensuring the polymer compositions and architectures. The use of density functional theory (DFT) methods for comparative modeling and visualization of organocatalytic ROP pathways, in line with experimental proof of the structures of the reaction intermediates, make it possible to establish these mechanisms. In the present review, which continues and complements our recent manuscript that focused on DFT modeling of coordination ROP, we summarized the results of DFT modeling of organocatalytic ROP of cyclic esters and some related organocatalytic processes, such as polyester transesterification.

Highlights

The development of biotechnology and medical technology has set higher requirements for biomedical materials
ring-opening polymerization (ROP), we summarized the results of density functional theory (DFT) modeling of organocatalytic ROP of cyclic esters and some related organocatalytic processes, such as polyester transesterification
Houk et al reviewed DFT modeling of the full diversity of organocatalytic processes in 2011 [29], the recent review of Jones [30] that addressed the contributions of quantum chemistry to the development of ROP looked at some of the aspects of organocatalytic polymerization of cyclic esters

Summary

Introduction

The development of biotechnology and medical technology has set higher requirements for biomedical materials. ROP catalysts, in the decades hundreds of metal complexes were studied in the polymerization of different cyclic substrates [1,2,17,18]. The synthesis of polyesters via the ROP of cyclic esters typically requires the monomer-to-catalyst ratios ~103 –104 [1,2,20]. Houk et al reviewed DFT modeling of the full diversity of organocatalytic processes in 2011 [29], the recent review of Jones [30] that addressed the contributions of quantum chemistry to the development of ROP looked at some of the aspects of organocatalytic polymerization of cyclic esters. This review complements our previous work that was devoted to the DFT modeling of coordination ROP that was recently published in the special issue of Molecules [32]

Polymerizability of Cyclic Esters

DBU and Related Compounds

Thiourea-Based Catalysts

Acid-Catalyzed ROP

Phosphazenes: A Regrettable Lacuna in DFT Modeling

10. Concluding Remarks